Since the discovery of oxidic high temperature superconduction, materials have been known which have superconducting properties at temperatures up to 125.degree. K. These materials are metallic oxide ceramics produced by sintering processes, i.e. very brittle and difficultly workable materials, which can only be brought into the forms necessary for technical applications with extreme difficulty. For many applications in the fields of electrical engineering and microelectronics, as well as for the manufacture of superconducting solenoid coils as energy stores there is a need for filamentary or strip-like conductors. These conductors are preferably to be manufacturable with diameters down to below 1 mm and with lengths up to several kilometers. Such conductors must be sufficiently flexible that they can be bent without suffering damage about a radius of approximately 20 mm. Particularly in connection with magnet construction, it is also important for the conductors to have a very high current density of above 10,000 A/cm.sup.2 in the magnetic field.
Under Prof. Dr. P. Wachter a dissertation or thesis was produced at ETH Zurich (Diss. ETH No. 10213, Joachim Lohle), describing filamentary conductors for high temperature superconduction. It does not in fact relate to a superconducting material shaped in wire or filament fort, but an enveloped, sintered, oxidic, superconducting ceramic material, particularly YBa.sub.2 Cu.sub.3 O.sub.x or Bi.sub.2 Sr.sub.2 CaCu.sub.2 O.sub.x. The filamentary superconductors are manufactured in that by multiple pressing, sintering and recomminution from the corresponding oxides, superconducting ceramic material is filled into a tube or sleeve and then the filled tube or sleeve is drawn in a per se known manner into a wire shape. So that the ceramic material has the desired superconducting properties in the completely drawn wire shape, it must again be sintered in this state (final sintering) under flowing oxygen.
Filamentary conductors with flat cross-sections (strips) are produced by rolling the not yet finally sintered, filamentary conductors and final sintering to the strip shape. The strips have higher current densities than the filamentary conductors with a circular cross-section, which is due to the compaction of the ceramic material and the crystallite orientation during rolling.
For drawing filamentary conductors, use is e.g. made of a metal tube with an external diameter of 10 mm and an internal diameter of 8 mm, into which is filled superconducting ceramic material and which is shaped by multiple drawing to a 0.5 mm external diameter and 0.4 mm internal diameter, a cross-sectional reduction of approximately 8% being obtained during each drawing stage.
According to an analogous method filamentary conductors and strips are produced with more than one superconducting core, in that the metal tube is filled with e.g. nine already drawn filamentary conductors in each case enveloping a core instead of being filled with the ceramic material. By filling a tube with already multicore, filamentary conductors the number of cores can be further increased.
In order that during the necessary final sintering the ceramic material can be brought into contact with the flowing oxygen, the sleeve material must have an adequate oxygen permeability. It is therefore proposed for the production of filamentary conductors to use e.g. silver tubes or palladium-alloyed silver tubes. Apart from an adequate permeability for oxygen, silver also has a sufficiently high melting point to allow a usable sintering temperature and is sufficiently chemically stable not to react during the sintering process with either the oxygen or the ceramic material. During the drawing of the filamentary conductors the silver sleeve is cold-worked and therefore becomes harder. Therefore during the aforementioned, exemplified drawing process between drawing stages, soft annealing must take place one or two times.
Highest demands must be made on the filamentary conductor quality, because defects can greatly influence superconduction. The filamentary conductors and, strips described in the aforementioned dissertation are produced by tiresome manual work, with costs which would be unacceptable for technical or industrial uses. The problems occurring for possible industrial manufacture and in particular with an acceptable drawing speed did not form the task of the aforementioned dissertation and are not referred to in any way therein.